Laminates comprising alkenyl substituted phenolic resins as binders



United States Patent LAMINATES COMPRISING ALKENYL SUBSTI- TUTED PHENOLIC RESINS AS BINDERS Roger M. Christenson, Whitefish Bay, Wis., and Richard A. Freeman, Rockford, Ill., assignors to Pittsburgh Plate Glass Company Application March 9, 1954, Serial No. 414,976

6 Claims. (Cl. 154--2.6)

This invention relates to a resinous product comprising a reinforcement of fibrous material embedded in or coated with a heat converted resin and to a method of preparing the same; the invention has particular relation to a product of the foregoing type in which the resin is derived by heating a condensation product of an aldehyde and a phenol, said phenol containing an ethylenically unsaturated side chain.

*It has long been recognized that valuable heat convertible polymeric products can be obtained by condensation of an aldehyde such as formaldehyde (or a substance reacting to produce the same) with a phenol free of functioning groups other than phenolic hydroxyl groups. The reaction apparently involves elimination of water through condensation between the hydroxyls and the carbonyl groups of the aldehyde. The overall eifect of the reaction is to build up macromolecules to provide thermoset resinous products.

It has also been suggested to employ liquid condensation products of the foregoing phenols and aldehydes to soak or to coat sheets of fibrous materials such as fabrics, paper mats, or similar fibrous bodies. These, with, or without subsequent stacking of the sheets as laminates, were confined under pressure, between suitable surfaces to cure them to hard thermoset state. Bodies thus formed, were valuable as dielectrical materials and could be used as supporting panels or as coatings, or coverings for electrically charged bodies of various types. However, most of the phenolic condensation products as previously prepared, have not been entirely satisfactory in certain respects. For example:

Most of them tended to be slow in curing and required either an excessive period of time for the cure, or else they required the application of heavy pressure to arrive at a satisfactory degree of molecular aggregation within a reasonable period of time.

Many of them were low in such physical values as tensile strength, fiexural strength, impact strength, and molulus of elasticity. This was especially true of those materials having good dielectric properties.

The dielectric strength also was such that it was necessary to accept a value of 500 to 340 volts/mil for short application, or 360 to 250 volts/mil for step-by-step application, as standard.

. The previously known products were often of poor gloss and tended to be objectionably discolored.

In copending applications of Roger M. Christenson, Lowell O. Cummings and Alfred R. Bader, entitled Phenolic Resins, Serial Numbers 390,088 and 390,089, filed November 13, 1953, it is disclosed to form resinous condensation products of aldehydes such as formaldehydes and mixtures of phenols containing alkenyl side chains in the presence of an acid or preferably an alkaline catalytic agent. By use of such process, liquid or soluble resin intermediates are obtained, which contain ethylenically unsaturated side chains and which presumably,-

have a capacity for addition reaction whereby to induce formation of macromolecules characterizing a resin.

It has now been discovered that valuable materials having excellent dielectric properties can be formed by appropriate incorporation of the foregoing condensation products as bonding agents into one or more layers of fibrous materials such as sheets of paper or various fabrics in order to provide valuable dielectric materials which can be used as panels for electrical instruments and parts or for insulatively covering electrical parts and apparatus. Articles involving fibrous materials bonded with the resins are exceptionally light in color, a property which apparently is not found in articles employing other phenolic resins as bonding agents.

For a better understanding of the invention, reference may now be had to the accompanying drawings in whichlike numerals refer to like parts and in which Figure 1 is a fragmentary side view of a laminated electrical panel constructed in accordance with the provisions of this invention.

Figure 2 isan elevational view of the construction shown in Figure 1.

embedded in and bonded together by the resinous material, as hereinafter described. But three plies are shown; however, it will be apparent that this number can be increased or decreased as desired.

Phenols containing alkenyl substituted side chains suitable for condensation with aldehydes such as formaldehyde (or formaldehyde yielding substances) to provide r'esinifiable materials, can be obtained by reacting a phenol containing a free hydrogen atom in the ring with a conjugated diene such as butadiene under appropriate conditions. In preparing condensation products of aldehydes such as formaldehyde and alkenyl substituted phenols such as mixtures of butenylphenols, for use as binding agents for the fibrous materials in the dielectric products of this invention, relatively pure alkenylphenols such as orthoor para-alkenylphenols or di or trialkenylphenols may be employed. However, it is usually preferred and more economical to employ mixtures of the alkenyl substituted phenolic compounds.

The proportions of the various permissible alkenyl compounds with respect to each other, are susceptible of relatively wide variations. Ordinarily, the predominate component of the mixture is one or more monoalkenylphenols including orthoand para-monoalkenylphenols and preferably the monoalkenyl component constitutes about 55 to percent by weight of the total mixture. The balance of the mixture (about 15 to 45 percent by weight) is composed primarily of diand trialkenylphenols, although phenolic materials including polyphenols such as alkenyl substituted dior triphenol may be also present in an amount depending upon the method by which the alkenylphenol mixture is prepared.

Mixtures of alkenylphenols suitable for reaction with such aldehydes as formaldehyde (or formaldehyde yielding substances) by condensation, to form useful binders in the sheet products of this invention, are readily obtained by the methods described in copending applications, Serial Number 300,359, filed July 22, 1952, and Serial Numbers 337,226, 337,227, 337,228, now abandoned, and 337,229, now abandoned, all filed February 16, 1953.

The methods of preparing alkenyl substituted phenols described as the phenolic component in these copending applications, involve the reaction of conjugated dienes with phenolic compounds in the presence of certain catalysts such as Friedel-Crafts compounds, or Lewis acids. For example, the reaction product obtained by the an aqueous sulfuric acid catalyst is generally composed of less than about percent unreacted phenol, less than about 5 percent of ethers, 55 to 70 percent-by weight of monobutenylphenols and 15 tov 40 percent of the higher boiling phenols including die and tributenylphenols and polyphenol's. Ordinarily, the unreacted phenol and ethers will be removed from the reaction mixture by distillation before the condensation reaction with an aldehyde is carried out; however, this is not a critical step and condensation reaction takes place readily even though the unreacted phenols and' ethers are not removed. Mixtures containing smaller quantities of monoalkenylphenols and larger quantities of the higher boiling Phenols, for example, about 50 percent of monoalkenylphenols and 30 to' 50percent of higher boiling phenols. and the balance polyphenol's' and ethers, mayalso be employed with goodresults, as may mixtures containing no mono-v alke'nylphenols.v Also, the mixtures may be composed entirely of 'ortho-' and para-monoalkenylphenols. and in fact, excellent resins are obtained when such a mixture is employed. Mixtures of alkenylphenols with other phenols containing no unsaturated side chain, such as phenol, butylphenol, amylphenol and the like may be employed in thefpreparation of thermosetting compositions for use in the preparation of fiber-reinforced dielectric products of this invention. e 7

While the foregoing techniques are usually preferred inthe preparation of mixtures of alkenylphenols and such mixtures so prepared may be reacted with formaldehyde to provide thermosetting'condensationv products of exceptional merit in the dielectric art it is to be understood that other methods may sometimes be employed to provide useful mixtures of alkenyl substituted: phenols. This, invention includes the use of suchother mixtures of phenols where the latter are of the character of those above described, regardless of the method by which they are obtained.

As illustrative of the alkenyl substituted phenolic compounds, whichsi'ngly, or preferably in mixtures, are condensed with an aldehyde such as formaldehyde (or a formaldehyde yielding'compound) to form the novel resins that can be applied to fibrous reinforcement to form the novel sheet materials of the, present invention, there are set forth below the products of the reaction of butadiene- L3 and phenol:

III

0H 7 p Z wrec ed-"cm,

r kw cml V m The above structures are'all readilytobtained by the reaction of phenolic compounds with conjugated dienes in accordance with the methods described injthe copendingl applications. 7 r a r Phenolic compounds which may be reacted with conjugated dienes and notably butadiene, to give compounds of the above structures include: phenol, catech'ol, resorcinol,- pyrogallol, tertiary. butyl catechol, beta-naphthol, guaiacol, 0-, mand p-cresol, 2,3- xylenol, 2,5-xylenol, 3,4-xylenol, and the like alkyl substituted phenols, bis- (4 -hydroxyphenyl) 2,2-propane, and the like. 3

Typical conjugated dienes which react. with phenolic compounds to form the desired mixture of alkenylphenols include butadiene-1,3, 2- methylbutad iene-1,3, piperylene, 2-methyl-pentadiene-L3, hexadiene-l,3, 1-. chloro-2-methylbutadiene-1,3, cyclopentadiene, and thelike. However, butadiene is presently preferred and is particularly emphasized.

The preferred alkenylphenolic compounds for condensation with aldehydes in accordance with the present invention are mixtures of monohydric compounds, name'- ly, the hutenylphenols, including orthoand para-2- butenylphenols, di-Z-butenylphenol and tri-Z-butenylphenol. However, mixtures. of other alkenylphenolic compoundsmay also be used, including butenylcresols, butenylcatechols, butenyl-2,S-dichlorophenols, butenyl- 2,5-di'nitrophenols, butenyl-2,3-dimethoxyphenols, mono-,

di and tributenyl resorcinol, mono-, diand tributenyl-- guaiacol, 2-chlorobutenylcresol, Z-chlorobutenylphenol, 2f-iodobutenylphenol, orthoand para-cyclopentenylphenol, pentenylphenol, pentenylcresol, pentenylguaiacol, halopentenylphenols, halopentenylguaiacols, and the like (halogen may be chloro-, bromoor the like);

Itmay be, that the tributenylphenols, where they are present in the mixtures, do not actually condense with aldehydes, at least to the same extent as do the monoanddialkenylphenols, but instead react through the unsaturatedjinkages or by other mechanism. This type of reaction'is, of course, not possible with conventional phenols and this fact, may account, at least. in part, for the improved electrical properties. and faster cures characterizing .the' thermosetting compositions, when they are employed as binder resins for reinforcing fibers of. various types.

In'th'e preparationcf theyconclensation products which are used in the practice of the present invention, any aldehyde may be utilized to. provid e' roducts of utility. However, aldehydes containing only atoms of carbon, hydrogen, and oxygen and"particularly-formaldehyde, are

preferred. In place of formaldehyde, a material which decomposes upon heating to yield formaldehyde, or which otherwise reacts to produce the same products'with the phenolic compounds asformaldehyde, may be employed.

Such aldehyde-yielding compounds include paraformaldehyde or trioxymethylene. An aqueous 37' percent solu tion of formaldehyde is; generally used very'successfully.

In carrying; out the condensation involved. in, the. preparation of the binder resins, various catalytic agents. may

be employed. For example, acids may be employed.

However, the alkaline catalysts are usually preferred. Suitable, alkaline catalysts: include: sodium hydroxide, potassium hydroxide, ,barium. hydroxide; sodiumv carbonate,

' potassium carbonate. ammonia hexamethylenetetramine and; the like. These alkaline materials efl'ec'tively pro.-

duce' a condensation reaction between; the alkenylphenol and the aldehyde. to provide liquid, or soluble products.

which whenapplied as binders to various fibrous materials; can lie-cured by application of'heat and" pressure to .of light color, which is within itself, a Surprising result since it has previously been. contended that alkalne materials were the cause of the objectionable color in resinous products. q

The quantity of alkaline catalyst employed in the condensation reaction is, generally, such that about equivalent of catalyst is present for each equivalent of alkenyl phenol compound. 1 Based upon the total weight of reactants, about 0.5 to about 5 percent of the alkaline material is utilized. Large amounts ofthe catalyst may be employed if desired, but, of course, the use thereof tends unduly to increase the expense involved in the reaction without added advantages in other respects.

While useful thermosetting condensation products are obtained with a relatively wide range of molar ratios of aldehyde to alkenylphenols, it has been found that the best products for use in the formation of impregnates for use in the electrical art are obtained when about two moles of an aldehyde such as formaldehyde are utilized for each mole of the alkenylphenolic compounds in the reaction mixture. For some applications, however, the lower limit of aldehyde may be about 0.5 to 1 mole per mole of the alkenyl phenol and the upper limit of the aldehyde ratio may be as high as about 5 moles per mole of the phenolic compound; For most purposes, these extremes are not desirable. Usually, when the aldehyde content is dropped substantially below about 1.5 moles per 2 moles of the phenolic compound, the resinous products If the ratio of first admixing the alkenylphenols and the catalysts under non-oxidizing conditions, e. g. under an inert atmosphere such as nitrogen and/or in the presence of a reducing agent such as sodium hydrosulfite, while the reaction mixture is cooled to maintain the temperature at about room temperature (25 C.). The aldehyde is added slowly at this temperature level until solution of the phenolic component is obtained, after which the temperature is allowed to rise to 35 C., at which level it is maintained until the remainder of the aldehyde is incorporated. Dur

ing the period of the reaction, care should be taken to keep traces of air out of the reactor at all times. The reaction is allowed to proceed for about 48 hours at room temperature.

At the end of this time, the reaction mixture is carefully acidified to a pH of about 5 with a mineral acid such as hydrochloric acid, or sulfuric acid, or with a carboxylic acid such as acetic acid, or propionic acid. During the acidification two layers are formed, one being a water layer and the other an alkenylphenol resin layer. The water layer is drawn off and the water-insoluble layer of resin is water-washed four or five times.

At this point, it is advantageous to add about 0.1 percent by weight, based upon the resin, of a sequestering agent such as aminotetracarboxylic acids such as ethylenediamine tetraacetic acid which form non-reactive complexes with any iron in the reaction mixture. The latter element, which if free, or otherwise present in active form, would produce instability with resultant darkening of the product, is thus bound and in effect, is eliminated from the system.

Resin products may be freed of water by application of vacuum stripping under a pressure of about 20 to 55 mm. (absolute). Alternatively, water may be removed by adding xylene or toluene or butanol to the condensation product and conducting an azeotropic distillation. They may, also, be blown with inert gas (CO orN to remove water. t

The resinous products prepared by the foregoing techniques are generally recovered as viscous liquids which with, or without dilution, can be employed to impregnate sheets and mats of fibrous materials such as alpha-cellulose or fiber glass to provide valuable dielectrics, under the provisions of the present invention.

While the .above described method, for carrying out the condensation is preferred, particularly when the alkenylphenol mixture is a mixture of butenylphenols, other methodsof carrying out the condensation may be employed. For example, useful liquid condensation products which can be employed to impregnate or to coat fibrous materials may be obtained simply by admixing the reactants and an acid or alkaline catalyst and allowing the mixture to stand at room temperature for-about .48 hours, ,or by maintaining the reaction mixture at a products may be employed to bond fibers in the preparation of useful dielectrics.

The preparation of butenylphenols which can be condensed with aldehydes such as formaldehyde in the pres- .ence of an alkaline catalyst to form liquid resins suitable for use as bonding agents in the preparation of dielectrical materials is illustrated by the following examples:

EXAMPLE A A 54 gram quantity (1 mole) of butadiene-1,3 in 100 milliliters of toluene was added to a mixture of 94 grams (1 mole) of phenol containing 100 milliliters of toluene, 23 grams of polyphosphoric acid and 10 grams of percent syrupy phosphoric acid, to initiate an exothermal reaction. The reaction mixture was then cooled to room temperature and was stirred for 14 hours to provide a condensation product which was washed with water and the mixture was fractionally distilled. A mixture comprising 60 grams of monobutenylphenols, namely, orthoand para-butenylphenols and minor quantities of diand tributenylphenols was obtained. The mixture was suitable for incorporating with aldehydes such as formaldehyde together with alkaline catalysts and condensation to provide liquid resins that could be employed to impregnate paper or glass fabrics. The impregnates, when cured, are of excellent dielectric properties.

EXAMPLE B In this example, 28 grams of titanium tetrachloride were added to a mixture of 94 grams (1 mole) of phenol, 65 grams (1.2 moles) of butadiene-l,3 and 200 milliliters of toluene cooled to a temperature of 10 C. An exothermic reaction resulted and the reaction mixture was maintained at room temperature for 16 hours. The reaction mixture was washed to remove the catalyst and was subjected to distillation under reduced pressure. A yield of monobutenylphenols of about 85 percent, together with minor quantities of diand tributenylphenols, was

. obtained.

This mixture, like that from Example A, was suitable for condensation under alkaline conditions, with aldehydes, e. g., formaldehyde, to form liquid resins, useful for impregnating fibrous sheets in forming valuable dielectrical bodies which often are of unusually light color.

EXAMPLE C In the performance of this example,-17 pounds of toluene, 17 pounds of phenol and 28.8 pounds of 67.2

was decanted the remainder of the reaction mixture was distilled to strip-off excess water, formaldehyde and ammonium hydroxide. The product was a liquid of a solidscontent of 94.2 and was useful in forming fiber reinforced dielectrics in accordance with the present invention.

EXAMPLE G-7l 1 A glass lined reactorwas charged with the following mixturez t Pounds Mixed butenylphenols (monobutenylphenols, di-

1 and tri-butenylphenols) 24.6 Formaldehyde (37 percent aqueous solution) 27 Sodium hydroxide r t i 1.7 Water 1.7 Sodium hydrosulfite 0.12

The resulting mixture was cooled to 75'", to 80 F. and was agitated for 5 hours, after which it was allowed to stand for, 43 hours It was then acidified to a pH of 5 with 68 percent sulfuric acid and was allowed to stand 1 until a water layer settled out. The water layer was drawn-01f and discarded and the wet resin (36.25 pounds) was treated with 0.04 pound of an amino tetracarboxylic acid known commercially as Sequestrene AA. The resin was heated to 220 F. and was stripped with inert gas (nitrogen) until a Gardner viscosity of W at 75 percent solids in normal butanol was reached. The resin was then thinned with pounds of butenol and was filtered at 110 F. The product was of the following characteristics:

Weight per gallon-8.45 pounds.

Solids-62.2 percent at 110 C.

ViscosityQ to R on the Gardner scale.

This product was a valuable material for impregnating fibrous materials such as alphacellulose or glass fibers and could be applied by spraying, or dipping, to sheets of the latter materials.

The resultant impregnates could be cured by baking, thus forming useful dielectric bodies.--

EXAMPLE H-S The resinifiable charge in this example comprised:-

Grams Mixture of pentenylphenols 1620 Formaldehyde (37% aqueous solution) 100 Sodium hydrosulfite 8 Sodium hydroxide (50% aqueous solution) 200 The mixture was charged into a glass reactor where it was stirred, with exclusion of air, for 48 hours at a temperature of to C. The reaction mixture was acidified with'70 percent sulfuric acid until a pH of 5 was reached. The water layer which had formed, was drainedolf and 2 grams of Sequestrene AA were added to the resin layer. The resin layer was then dried by blowing with an inert gas for 3 hours at 100 C. to provide a resin having a viscosity of Z6. This resin with, or without thinning, could be employed to coat or impregnate fibrous materials. Useful dielectrics could be formed by-baking the impregnates.

The foregoing condensates of butenylphenols and formaldehyde when employed to coat or impregnate fibrous materials are characterized by numerous exceptional properties. For example, the rate of cure when the bodies are subjected to heat and pressure is quite rapid, good cures being obtained in many instances in 30 minutes to 60 minutes. Other comparable condensation products often require several hours. Many of the products are characterized by exceptionally high dielectric strength, high mechanical strength, exceptionally light color and plified in the preceding Examples A-l through H-S tests were conducted in the following manner.

EXAMPLE I Sheets of alphacellulose paper, much like a conventional decorative paper, were soaked'in a liquid condensation product of a bu-tenylphenol and formaldehyde prepared in accordance with the provisions of Example A-l, a number of hours beingallowed in order to assure thorough soaking, although 15 or 20 minutes is usually adequate for the purpose. The sheets of wet paper were laid against. .a nearly vertical glass plate and excess resin was removed with a rubber squeegee roller. The sheets of paper were: then reversed on theglass and the opposite sides were likewise rolled to remove anyex-cess resin adhering thereto.

The sheets weresubsequently stretched across a frame and the resin content thereof was precured in an oven at 350 F. for 10 to lSgminutes; It was determined that approximately 12 minutesconstituted an optimum precure time which, whenernployed, resulted in sheets in which the resin had liquid flow and cohesiveness to produce excellent laminates inthe subsequent curing and pressing operation (to be described) but at the same time the sheets were notso excessively tacky as to prevent, or hinder manipulation thereof in the laying up operations involvedin forming the laminates.

' -A number ofthese partially cured sheets were laid up to form laminates of desired thickness and were then cured for one hour ina press at 300 to 320 F. under a pressure between 1 50 and 300 pounds per square inch. A series of runs were conducted in the manner above described and the times, temperatures and pressures employed are tabulated as follows:

Precure Pressing Run 7 a Time Temp., Time, Temp., P. s. i. e le, 15 350 1 300-320 334. 7 15 350 1 300-320 334. 7 10 350 v1 300-320 229 10 350 1 300-320 220 The products were of attractive, light yellow color having surfaces of high gloss, especially where they are of high resincontent. The colorin laminates of this type is regarded as being unusual; in so far as is presently known, no other phenolic resin will form corresponding laminates of such light color. Therefore, theyare excellently adapted for use in applications where color is important. The products also have high mechanical strength and good dielectric properties.

These productswere tested and compared with the standards for paper base laminates as established by the National Electrical Manufacturers Association in their public'ation No. LPI-l, September 1951, and were found comparable to the better grades of electrical insulators as represented by the codes XXP, XXX, and XXXP, page 8 of that publication, but. were greatly superior in tensile strength and dielectric strength, as determined for either short period, or stepwise application. The properties of condensates of butenylphenol, together with the corresponding standards, as established by the foregoing association, are hereby tabulated as follows:

ifurtherglist qfj:tne;sezeral g ades; fsresinsiandi h cati ns tfq iwh chi he 1a adsPt la a-asienw '3 Requains ade X ages-sis Mechanical s Mechanical hot punching.; P Mechanicalcold puriehingror shearinge P0 Electrical-arid-mechanicale e l e XX C-otton; fabric weighing-less than- 4 ozrused infine' machining applications- L Same as L but for electrical*applicationsrequiring Continuous filamentitype glass cloth,- general-pur-' a pose grade- 'GS ,In .general, .,the resins herein ,1 disclosed, eats least .subtantially,meetgthestandards, setup for the. classes. :Qften jtheyareimuch superior,tQtheSestandards. Such a..=vyide ,versatility ,inha, single family (of resins; is unusual.

EXAMPLEPII In this example, the fibrous reinforcement was a cloth of fine g1ass fibersvsuch'as isconventionallymsed infthe preparation. ofima-nyv laminates employed inathe aircraft industry and for similar applications, iwhere high nstrengthlis ,a prerequisite. vThe, liquid: resin employed was. ess.entially..'the same. as that :obtaineduin Example 1 G'7. Sheets of the glassifiber clothswere'i-mmersedin t the liquid resin, wereQsqueegeed on sa glass j plate :and ,wereprecured for ;10 minut,es at 350 1wo lamiates were subsequently? laid up, ortend-.12 plies, "the other ,0fe.14 plies. V'Lhe se -were,,cur ed for 6,0- minutesiat @Iemnerature of 300,F. ;The, pressure in the, mold :was jslight, ,(about. 10.ton30.-ip,,:s. i.). .The moldclosed-comln'Eh forms .of the invention as herein disclosed are to beiconsideredtaszbeingibyflvay ofiillustration and not iofilimitationa. It .wilLheapparent that numerous anodifictitious maynbelanade::tlrereinawithout,rdeparture ir'on "me spirit. Qf.the,jnyention-or the-scope' of the appended claims. 7 M V is r:

dwelclaima. a it V 1 A laminate 10f high tensile strength, high dielectric -stren g"th and'- light color; comprising :iafibrous sheet of fibers -which are-'bonde'd by condensationg'productsformed in th iabsenete of freeoxygen and free iron'andfb'eing (if-" about- 015 -to 5 mo lesof formaldehyderand2 inoles (if a**butenyl phenol -mixtur ef obtainedbyj, substitution "of hydrogen in the' -"b'enz'enering ofphenol "through reacltiongof phen'ol with bu'tadie'ne f-:in "the presence of p a pletely (that is to the limit .ofhtravel-iof .--the;sections where the-mold "stops came together and-prevented further mold-gravel. i jibe-properties of the curedlaminates are tabulated s .fOHOWs:

lam n e N9- 7 I FZI Flexural strength, p; s. L--.

Modulus of elasticity "(flexur .Tensile strength n-is.Vi

Modulus of elast city (tensile)-,.p i 'Elongatiom: percent. sflompressionstrengthcp Water ahsorptiommeree, Izod, FL-lbsz/inph (notch) Resin content; percent-" Har s ,Barc0l.-.--,--, Flame resistance 5-Bot1h ofi these products were of 'hi'ghmodulusqdfielastieity' and in general "were of j good properties adapting them for 'use wherever such j good; properties'fwere. de-' sirable. 'j'Ihe;col 1-wasfgood. M p

v 'The;glass cloth reinforced Jaminates are good "dielectrical-mateiiais. Laminatedstructuralelements'such as airplane parts and various otherstructural elements may be formed in like manner. V I

.In'; the formulation of "laminates embodyingglassj'fiber cloth impregnated-with butenylphenol formaldehyde j conden'sation products, *it'iSICQIISideICd 'thatthe percentage of the condensation' product in the ,ilaminate' 'may. 'be varied within a rangessoflabout 10 to 70 percent by weight, gdependent somevsihatupon the applications to' which the laminates tiffiz tpfibfi subjected. "It is considered that a very satisfaetonyall-around material can be obtained with ;about 320 percent by weight of resin in :Friedel Erafts ctttiflyst, the butenyl phenol 'niixture consistingmrimarily-o'f compounds of the *formulae:

and

{0H .;e rp. .cm 11H 2. A body a of light color, hightensile strength and high dielectric :strength comprising "a fibrous 'sheetmaterial containing a binder which isa' thermoset'con'densationiproduct of about 1.5' moles of formaldehyde and about 1 mole of phenolmixture consisting mainlycf 'the following components:

- H and 0Hro='c-'-o m said condensation product being jforme'd u-ndernon-oxi dizingrconditionszandain the substantial abs e'nceof=re actnr l1'ron.' l, t

,AebodyI-rof light -color, high'tensile strength and highxlielectricrsnzength comprisinga sheet of fibrous materialicomaining a ltherm'oset binder'-- -Which is a -condensaztion product zformeil iunder non oxidizing condi- Lions andzirrithe substantial i-absence (Sf-reactive iron-and bQi-Hgscomposridhfiabout 1 :5 moles df 'formaldehyde-and aantixmreaofsa-bont lfmoles of alk'enyl phenols derived by the reaction of phenolfand gbutfidiene-in the presence of;az liiedelzCfnaftszpatalyst;said 'henols consis'tingmainlyeof ?thesfnllowing'zcompoundsz w l 3 9:? 7 -cHq-ig.o,= z-aont m L laser-a erse to 13 4. A body of high tensile strength, high dielectric strength and light color, comprising a sheet of alpha cellulose fibers containing as a binder, a thermoset resin which is a condensation product in an alkaline medium under non-oxidizing conditions and in the substantial absence of iron, of about 1.5 moles of formaldehyde and about 2 moles of mixed alkenyl phenols obtained by addition reaction of phenol and butadiene in the presence of a Friedel-Crafts type catalyst, said mixture of phenols consisting mainly of the following components:

and

14 said condensation product being formed under nonoxidizing conditions and in the substantial absence of reactive iron, precuring the condensate while the sheets are separate from each other for about 10 to 15 minutes but to a state in which they are still cohesive, stacking the sheets and completing the cure to form said laminate.

6. A method of forming a laminate of fibrous sheets comprisingthe steps of impregnating a plurality of sheets of alpha cellulose with a liquid condensation product formed under non-oxidizing conditions and in the substantial absence of reactive iron, the condensation product being of about 1.5 moles of formaldehyde and about 2 moles of two butenyl phenols respectively of the forand OH-.-C=CCH:

partially precuring the condensate while the sheets are separate, stacking the sheets and completing the cure.

References Cited in the file of this patent UNITED STATES PATENTS 2,006,043 Dykstra June 25, 1935 2,175,393 Hentrich Oct. 10, 1939 2,415,763 Ryan Feb. 11, 1947 2,587,578 Jones Mar. 4, 1952 2,631,140 Bloch Mar. 10, 1953 2,675,335 Rankin et al Apr. 13, 1954 

1. A LAMINATE OF HIGH TENSILE STRENGTH, HIGH DIELECTRIC STRENGTH AND LIGHT COLOR, COMPRISING A FIBROIUS SHEET OF FIBERS WHICH ARE BONDED BY CONDENSATION PRODUCTS FORMED IN THE ABSENCE OF FREE OXYGEN AND FREE IRON AND BEING OF ABOUT 0.5 TO 5 MOLES OF FORMALDEHYDE AND 2 MOLES OF A BUTENYL PHENOL MIXTURE OBTAINED BY SUBSTITUTION OF HYDROGEN IN THE BENZENE RING OF PHENOL THROUGH REACTION OF PHENOL WITH BUTADIENE IN THE PRESENCE OF A FRIEDEL-CRAFTS CTALYSTS, THE BUTENYL PHENOL MIXTURE CONSISTING PRIMARILY OF COMPOUNDS OF THE FORMULAE: 